Silicone polymers with high refractive indices and extended pot life

ABSTRACT

Novel compositions and methods of using those compositions to form high refractive index coatings are provided. The compositions comprise a mixture of two silicone polymers, a catalyst, and an inhibitor for the catalyst. The preferred catalyst comprises platinum. Unlike prior art silicone systems, the inventive composition can be provided in a one-part form due to a substantially improved pot life. The compositions can be spin- or spray-applied, followed by baking to crosslink the polymers and form a cured layer. The inventive cured layers have high refractive indices and light transmissions.

The present application claims the priority benefit of U.S. ProvisionalPatent Application Ser. No. 61/714,542, filed Oct. 16, 2012, entitledSILICONE POLYMERS WITH HIGH REFRACTIVE INDEXES, incorporated byreference in its entirety herein.

GOVERNMENT FUNDING

This invention was made with government support under contract number70NANB10H012 awarded by the National Institute of Standards andTechnology. The United States Government has certain rights in theinvention.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is broadly concerned with novel, siliconecompositions having long pot lives and that can be formed into highrefractive index (“RI”) layers. The compositions are useful for formingsolid-state devices such as flat panel displays, optical sensors,integrated optical circuits, light-emitting diodes (LEDs), microlensarrays, and optical storage disks.

2. Description of the Prior Art

A high RI value is highly desired to minimize internal reflectionbetween compound semiconductor materials and the encapsulant materialsused in high-brightness light-emitting diodes (HB LEDs). Historically,the development of materials with high refractive indices (RIs) startedwith the use of sputtering to deposit inorganic anti-reflective coatingson optical lenses, which is a high-cost, low-throughput process. Sol-gelcoating technologies were developed to replace sputtering to produceinorganic films on the devices. However, sol-gel technologies involve acomplicated manufacturing process, and they have many problems withstorage stability and reliability. The optoelectronics industry isseeking more robust high RI materials that can be applied using existingequipment to achieve production at low cost and high throughput.

Various efforts to develop high RI materials have been undertaken, someinvolving the incorporation of heavy elements, such as bromine, orhighly aromatic structures to increase RI.

Organic-inorganic hybrid coatings have also been developed. However,these coatings undergo more than 60% shrinkage during the curingprocess, which leads to high film stress and susceptibility to crackingfor thicker films (>0.5 μm thick). The need for curing at temperatureshigher than 200° C. is also a limitation for some device applications.

In addition, vacuum-deposited and chemical-vapor-deposited (CVD) opticalcoatings have been utilized in optoelectronics applications for manyyears. These coatings are traditionally limited to thin-filmapplications and are expensive to apply.

Finally, prior art compositions (particularly silicone-containingcompositions) have short pot lives. That is, the ingredients must beprovided in a two-part system because they begin to react upon mixing,and gelling occurs shortly thereafter, making the composition unusable.As a result, the end user must obtain the composition in two separatecontainers and mix the composition at the point and time of use. Thecomposition must be used right away, before it becomes unusable. Thisresults in the need to carry extra inventory, as well as to carry outadditional steps during manufacturing, creating the potential for extraissues to arise with those steps.

SUMMARY OF THE INVENTION

The present invention broadly provides a method of forming an LED orother electronic or microelectronic structure. The method comprisesproviding a substrate having a surface; and forming a layer of acomposition on the surface of the substrate. The composition comprises amixture of first and second silicone polymers, wherein: the secondpolymer is different from the first polymer; and the composition has apot life of at least about 24 hours.

The invention further comprises an LED or other microelectronicstructure comprising a substrate having a surface and a layer of acomposition on the surface. The composition comprises a mixture of firstand second silicone polymers, wherein: the second polymer is differentfrom the first polymer; and the composition has a pot life of at leastabout 24 hours.

An LED or other microelectronic structure comprising a substrate havinga surface and a cured layer on the surface is also provided by theinvention. The layer comprises crosslinked polymers having a structureselected from the group consisting of:

where:

each R₁ is individually selected from the group consisting of alkylenes;and

each of R₂, R₃, R₄, R₅, R₆, and R₇ is individually selected from thegroup consisting of alkyls, phenyls, aromatics, and cyclic aliphatics.

Finally, the invention is also directed towards a composition comprisinga mixture of first and second silicone polymers, a catalyst, and aninhibitor. In the preferred embodiment, the second polymer is differentfrom the first polymer; and the composition has a pot life of at leastabout 24 hours.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The inventive composition comprises a one-part silicone formulation thatis highly stable and can be formed into high RI coatings. Thecomposition can additionally be formulated into nanocomposites tofurther increase the RI. The composition comprises first and secondsilicone polymers, wherein the second polymer is preferably differentfrom the first polymer.

The first polymer can be either a homopolymer or a copolymer. Preferredfirst polymers are vinyl-terminated siloxanes. It is also preferred thatthe first polymer be phenyl- and/or methyl-containing homopolymers orcopolymers of siloxane.

A preferred first polymer has a formula selected from the groupconsisting of

where:

each R₁ is individually selected from the group consisting of aikylenes(preferably C₁-C₈, and more preferably C₁-C₄); and

each of R₂ R₃, R₄, and R₅ is individually selected from the groupconsisting of alkyls (preferably C₁-C₈, and more preferably C₁-C₄),aromatics (preferably C₆-C₁₄, more preferably C₆-C₁₀, and even morepreferably C₆, i.e, phenyl), and cyclic aliphatics (preferably C₆-C₁₄,more preferably C₆-C₁₀, and even more preferably C₆).

In some embodiments, R₁ is absent. Additionally, x:y is preferably fromabout 100:0 to about 70:30, and more preferably from about 97:3 to about80:20.

Particularly preferred first polymers are selected from the groupconsisting of: (a) structure (I), where each of R₂ and R₃ is phenyl; andeach of R₄ and R₅ is -CH₃; and (b) structure (II), where R₂ is —C₃, andR₃ is phenyl. Specific examples of suitable vinyl-terminated siliconesfrom Gelest include PMV-9925, PDV-2331, PDV-0331, PDV-0325, and VDT-954.Specific examples of suitable phenyl- or methyl-containing polymersinclude PMV-9925 (a polyphenylmethyl homopolymer), the PDV silicones(diphenylsiloxane-dimethylsiloxane copolymers), and VDT-954 (avinylmethylsiloxane-dimethylsiloxane copolymer).

Regardless of the first polymer chosen, it is preferred that the overallsiloxane content be from about 85% to about 100% by weight, morepreferably from about 90% to about 99% by weight, and even morepreferably from about 93% by weight to about 98% by weight, based uponthe total weight of the first polymer taken as 100% by weight.

Preferably, the first polymer has a weight average molecular weight offrom about 2,000 Da to about 30 kDa, more preferably from about 10 kDato about 30 kDa, and even more preferably from about 10 kDa to about 15kDa. Additionally, the first polymer will preferably be provided insufficient quantities to be present in the composition at a level offrom about 85% to about 99.5% by weight, more preferably from about 95%to about 99% by weight, and even more preferably from about 96% byweight to about 98% by weight, based upon the total weight of thecomposition taken as 100% by weight.

The second polymer can also be either a homopolymer or a copolymer, andis preferably chosen so as to contain groups that will crosslink withthe first polymer under the desired conditions. Suitable suchcrosslinker second polymers include crosslinker siloxanes such hydridosiloxanes.

A preferred second polymer has a formula selected from the groupconsisting of

where each of R₆ and R₇ is individually selected from the groupconsisting of alkyls (preferably C₁-C₈, and more preferably C₁-C₄),aromatics (preferably C₆-C₁₄, more preferably C₆-C₁₀, and even morepreferably C₆, i.e., phenyl), and cyclic aliphatics (preferably C₆-C₁₄,more preferably C₆-C₁₀, and even more preferably C₆).

In a preferred embodiment, R₆ is phenyl, and R, is -CH₃. In anotherembodiment, each of R₆ and R₇ is —CH₃. Additionally, m:n is preferablyfrom about 100:0 to about 60:40, and more preferably from about 55:45 toabout 50:50.

Regardless of the second polymer chosen, it is preferred that theoverall siloxane content be from about 85% to about 100% by weight, morepreferably from about 90% to about 99% by weight, and even morepreferably from about 96% by weight to about 98% by weight, based uponthe total weight of the second polymer taken as 100% by weight.Additionally, the second polymer (crosslinker) to first polymerequivalent ratio is preferably from about 0.8:1 to about 1.2:1, and morepreferably from about 0.8:1 to about 1.0:1.

Preferably, the second polymer has a weight average molecular weight offrom about 500 Da to about 20 kDa, more preferably from about 1 kDa toabout 15 kDa, and even more preferably from about 5 kDa to about 15 kDa.Additionally, the second polymer will preferably be provided insufficient quantities to be present in the composition at a level offrom about 0.25% to about 15% by weight, more preferably from about 0.5%to about 5% by weight, and even more preferably from about 2% by weightto about 4% by weight, based upon the total weight of the compositiontaken as 100% by weight.

Examples of such crosslinkers for use as the second polymer includethose from Gelest such as HPM-502, HMS-992, HMS-501, HMS-064,polyhydrosilsesquioxane, and other hydride-containing copolymers orhomopolymers of dimethylsiloxane or phenyl-containing siloxanes.

The composition will preferably further comprise a catalyst. Thepreferred catalyst is one that comprises platinum. Particularlypreferred such platinum catalysts include those selected from the groupconsisting of platinum-divinyltetramethyldisiloxane catalysts andplatinum carbonyl cyclovinylmethylsiloxane complex catalysts.

The catalyst is preferably included in the composition at levels of fromabout 0.01% by weight to about 0.1% by weight, more preferably fromabout 0.5% by weight to about 0.1% by weight, and even more preferablyfrom about 0.4% by weight to about 0.9% by weight, based upon the totalsolids in the composition taken as 100% by weight.

The compositions will also preferably include an inhibitor, with theinhibitor being selected to coordinate with the catalyst. Even morepreferably, the inhibitor selected will coordinate with, or react with,platinum. Preferred inhibitors are volatile inhibitors such as ketones,alcohols and alkynes, such as those disclosed in U.S. Pat. No.4,184,006, incorporated by reference herein. Suitable alkynes include,for example, 2-methyl-3-butyne-2-ol, ethynylcyclohexanol,2-butyne,2-methyl-but-1-en-3-yne, and phenyl acetylene.

Other inhibitors are disclosed in PCT Publication WO 2011059462,incorporated by reference herein and include such compounds as pyridine,acrylonitrile, diallyl maleate, 2-methyl-3-buten-2-ol, organicphosphines and phosphites, benzotriazole, organic sulfoxides,aminofunctional siloxanes, ethylenically unsaturated isocyanurates,olefmic siloxanes, alkenynes, unsaturated carboxylic esters, andunsaturated carboxylic amides.

The inhibitor will preferably be provided in sufficient quantities to bepresent in the composition at a level of from about 0.05% to about 2% byweight, more preferably from about 0.25% to about 1% by weight, and evenmore preferably from about 0.4% by weight to about 1% by weight, basedupon the total weight of the composition taken as 100% by weight.

In a particularly preferred embodiment, the composition comprises verylow levels of conventional/typical solvents or diluents (e.g., PGME,PGMEA, propylene carbonate). Thus, the composition comprises less thanabout 5% by weight, preferably less than about 2% by weight, and evenmore preferably about 0% by weight solvents or diluents, based upon thetotal weight of the composition taken as 100% by weight.

The compositions are formed by simply mixing the above ingredients atambient conditions so as to create a substantially uniform mixture ofthe ingredients. It will be appreciated that the inventive compositionsare superior to the prior art in that they have a long pot life, so theycan be stored for extended periods without gelling or becoming unusable.As used herein, “pot life” means that the composition has not gelled andis still capable of being spin-applied at ambient temperatures and atspin speeds of from about 1,500 rpm to about 2,000 rpm without requiringdilution or other treatment to reverse the gelling. Compositions thathave not gelled will have a Brookfield viscosity that is within about25%, preferably within about 15%, and even more preferably within about10% of the viscosity of the same composition at one hour after it wasprepared. Furthermore, cured films prepared from the composition willhave an RI of at least about 1.5 at 400 nm if the composition still hasa good pot life. The inventive compositions have a pot life, asdescribed above, of at least about 24 hours, preferably at least about aweek, more preferably at least about a month, and even more preferablyfrom about six months to a year. Advantageously, selected siliconesystems even showed a pot life of 538 days and more.

The compositions are applied to a substrate by any known method to forma coating layer or film .thereon. Suitable coating techniques includedip coating, roller coating, injection molding, film casting, draw-downcoating, or spray coating. A preferred method involves spin coating thecomposition onto the substrate at a rate of from about 500 to about5,000 rpm (preferably from about 1,000 to about 4,000 rpm) for a timeperiod of from about 30 to about 480 seconds (preferably from about 60to about 300 seconds) to obtain uniform films. Substrates to which thecoatings can be applied include those selected from the group consistingof silicon, silicon dioxide, silicon nitride, aluminum gallium arsenide,aluminum indium gallium phosphide, gallium nitride, gallium arsenide,indium gallium phosphide, indium gallium nitride, indium galliumarsenide, aluminum oxide (sapphire), glass, quartz, polycarbonates,polyesters, acrylics, polyurethanes, papers, ceramics, metals (e.g.,copper, aluminum, gold), and semiconductors.

The applied coatings are then heated for a sufficient time and to asufficient temperature so as to cause the polymers to crosslink with oneanother and form a cured layer. This is typically accomplished by bakingat temperatures of at least about 90° C., and more preferably from about130° C. to about 150° C. for a time period of at least about 60 minutes(preferably from about 30 minutes to about 60 minutes). The crosslinkedpolymers comprise one or more of the following structure in the curedlayer:

The variables above are as defined previously.

Cured coatings prepared according to the instant invention will havesuperior properties, and can be formulated to have thicknesses of fromabout 15 μm to about 35 μm, and more preferably from about 20 μm toabout 30 μm. At these thicknesses, the cured coatings will have arefractive index of at least about 1.4, preferably at least about 1.5,and more preferably at least about 1.56, at wavelengths of from about375 nm to about 1,700 nm, and preferably about 400 nm. Furthermore,cured coatings having a thickness of about 100 μm will have a percenttransmittance of at least about 80%, preferably at least about 90%, andeven more preferably least about 95% at wavelengths of from about 375 nmto about 1700 nm, and preferably about 400 nm.

It will be appreciated that the inventive one-part system offerssignificant advantages over prior art two-part systems. Some of thoseadvantages include less labor, less material (i.e., one bottle insteadof two), easier inventory tracking, easier to use, no concerns aboutmicrobubble formation or other issues that take place when mixing attime of use, and enhanced throughput.

EXAMPLES

The following examples set forth preferred methods in accordance withthe invention. It is to be understood, however, that these examples areprovided by way of illustration and nothing therein should be taken as alimitation upon the overall scope of the invention.

Example 1 Polyphenylmethylsiloxane-Based Formulation in the Presence ofPlatinum-Divinyltetramethyldisiloxane Catalyst

A vinyl-terminated polyphenylmethylsiloxane (PMV-9925, Gelest,Arlington, Va.) in the amount of 5 grams was blended with 0.64 gram ofhydride-terminated methylhydrosiloxane-phenylmethylsiloxane copolymer(HPM-502, Gelest, Arlington, Va.). This blend was stirred for 10 minutesat room temperature. Next, about 0.055-0.06 gram of a 0.1% solution (10ppm) of platinum-divinyltetramethyldisiloxane catalyst (SIP6831.2.Gelest, Arlington, Va.) in propylene glycol monomethyl ether acetate(“PGMEA”) was added. After the catalyst was added, the blend was stirredfor 10 minutes at room temperature.

Films made from this formulation had refractive index (“RI”) values of1.577 at 400 nm and 1.53 at 700 nm, as well as k values of10.0023-0.00028 for the visible light wavelengths. The thermaldegradation temperature of the composition was 223° C. The formulationwas spin-coated on a silicon wafer for 60 seconds at 1,500 rpm, followedby baking for 60 minutes at 140° C. This formulation delivered a filmthickness of 13.6 μm and had a pot life of 7 days with a slight increasein film thickness at day 7 (14.5 μm).

Example 2 Polyphenylmethylsiloxane-Based Formulation in the Presence ofPlatinum Carbonyl Cyclovinylmethylsiloxane Complex Catalyst

This formulation was made by using the same reagents and amountsmentioned in Example 1, with the exception of using a differentcatalyst. That is, a 0.1% solution of a platinum carbonylcyclovinylmethylsiloxane complex in PGMEA (10 ppm; SIP6829.2, Gelest,Arlington, Va.) was utilized.

Films made from this Example 2 formulation had RI values of 1.57 at 400nm and 1.53 at 700 nm, as well as a k value of 0.0000 for the visiblelight wavelengths. The thermal degradation temperature of thecomposition was 226° C. The formulation was spin-coated on a siliconwafer for 60 seconds at 1,500 rpm, followed by baking for 60 minutes at140° C. This formulation delivered a film thickness of 14.5 μm and had apot life of 7 days, with a slight increase in film thickness whenanother film was made as described above at day 7 (15.8 μm).

Example 3 Polyphenylmethylsiloxane-Based Formulation in the Presence ofa Platinum-Divinyltetramethyldisiloxane Catalyst

This formulation was made by using the same amounts of PMV polymer andHPM-502 crosslinker as mentioned in Example 1 but with a greater amountof SIP6831.2 catalyst. That is, this formulation was made using 0.005gram of undiluted SIP6831.2 catalyst, a concentration of 1,000 ppm.

Films made from this PMV-based formulation had RI values of 1.57 at 400nm and 1.53 at 700 nm as well as a k value of 0.0000 for the visiblelight wavelengths. The thermal degradation temperature of thecomposition was 230° C. The formulation was spin-coated on a siliconwafer for 60 seconds at 1,500 rpm, followed by baking for 60 minutes at140° C. This formulation delivered a film thickness of 16.3 um and had apot life of 1 day. The formulation gelled on day 2.

Example 4 Polyphenylmethylsiloxane-Based Formulation in the Presence ofPlatinum Carbonyl Cyclovinylmethylsiloxane Complex Catalyst

This formulation was made by using the same ratio of PMV polymer toHPM-502 crosslinker as mentioned in the preceding Examples, but with agreater ratio of the platinum carbonyl cyclovinylmethylsiloxane complexcatalyst than used in Example 2. Specifically, this formulation was madeusing 0.005 gram of undiluted SIP6829.2 catalyst, giving a catalystconcentration of 1,000 ppm.

Films made from this PMV-based formulation possessed RI values of 1.57at 400 nm and 1.53 at 700 nm, as well as a k value of 0.0000 for thevisible light wavelengths. Thermal degradation temperature of thecomposition was 245° C. The formulation was spin-coated on a siliconwafer for 60 seconds at 1,500 rpm, followed by baking for 60 minutes at140° C. This formulation delivered a film thickness of 15.5 μm, but onday 2, the film thickness increased to 21.7 μm when another film wasmade as described above, and the formulation gelled on day 3.

Example 5 Polyphenylmethylsiloxanc-Based Formulation in the Presence ofa Maleic Acid Diallylester Inhibitor andPlatinum-Divinyltetramethyldisiloxane Catalyst

PMV-9925 (same vinyl-terminated polyphenylmethylsiloxane as the previousExamples) in the amount of 5 grams was blended with 0.64 gram of HPM-502(the hydride-terminated methylhydrosiloxane-phenylmethylsiloxanecopolymer used in the previous Examples). This blend was stirred for 10minutes at room temperature. Next, 0.005 gram of a maleic aciddiallylester inhibitor (SL6040-D 1, Momentive Performance, ColumbusOhio) was added, and the mixture was stirred for 10 minutes at roomtemperature. Finally, about 0.005 gram of undiluted, as-receivedSIP6831.2 catalyst was added, and the blend was stirred for 10 minutesat room temperature.

Films made from this PMV-based formulation had RI values of 1.56 at 400nm and 1.53 at 700 nm, as well as k values of 0.0000-0.00159 for thevisible light wavelengths. The thermal degradation temperature of thecomposition was 223° C. The formulation was spin-coated on a siliconwafer for 60 seconds at 1,500 rpm, followed by baking for 60 minutes at140° C. This formulation delivered a film thickness of 17.2 μm. Theformulation had a pot life of 1 day and gelled on day 3.

Example 6 Polyphenylmethylsiloxane-Based Formulation in the Presence ofPlatinum Carbonyl Cyclovinylmethylsiloxane Complex Catalyst and a MaleicAcid Diallylester Inhibitor Inhibitor

This formulation was prepared by following the same procedure and usingthe same amounts of reagents as indicated in Example 5 but with 0.005gram of undiluted, as-received SIP6829.2 catalyst (instead of SIP6831.2catalyst).

Films made from this PMV-based formulation had RI values of 1.57 at 400nm and 1.53 at 700 nm as well as k values of 0.0000-0.00116 for thevisible light wavelengths. Thermal degradation temperature of thecomposition was 229° C. The formulation was spin-coated on a siliconwafer for 60 seconds at 1,500 rpm, followed by baking for 60 minutes at140° C. This formulation delivered a film thickness of 16.21 μm, whichincreased to 21.4 um on day 7 and 24.9 μm on day 8, when additionalfilms were made as described above. On day 9, the sample exhibited afilm thickness of 39.8 μm, and the formulation gelled on day 10.

Example 7 Diphenylsiloxane-Dimethylsiloxane Copolymer-Based Formulationin the Presence of Hydride-TerminatedMethylhydrosiloxane-Phenylmethylsiloxane Copolymer Crosslinker

Vinyl-terminated diphenylsiloxane-dimethylsiloxane (PDV-2331, Gelest,Arlington, Va.) in the amount of 5 grams was blended with 0.1665 gram ofhydride-terminated methylhydrosiloxane-phenylmethylsiloxane copolymer(HPM-502). This blend was stirred for 10 minutes at room temperature.Finally, 0.005 gram of undiluted, as-received SIP6831.2 catalyst wasadded. After the catalyst was added, the blend was stirred for 10minutes at room temperature.

This PDV-2331-based formulation had RI values of 1.53 at 400 nm and 1.50at 700 nm as well as k values of 0.0032-0.0039 for the visible lightwavelengths. The thermal degradation temperature of the composition was344° C. The formulation was spin-coated on a silicon wafer for 60seconds at 1,500 rpm, followed by baking for 60 minutes at 140° C. Thisformulation delivered a film thickness of 27.9 μm and had a pot life of1 day. The formulation gelled on day 2.

Example 8 Diphenylsiloxane-Dimethylsiloxane Copolymer-Based Formulationin the Presence of HMS-501 Crosslinker

Low-molecular-weight (10,000-15,000 Daltons) vinyl-terminateddiphenylsiloxane-dimethylsiloxane (PDV-2331, 1000-1500 cSt) in theamount of 5 grams was blended with 0.11 gram oftrimethylsiloxane-terminatedmethyl hydrosiloxane-dimethylsiloxanecopolymer (HMS-501, Gelest, Arlington, Va.). This blend was stirred for10 minutes at room temperature. Next, about 0.005 gram of undiluted,as-received SIP6831.2 catalyst was added. After the catalyst was added,the blend was stirred for 10 minutes at room temperature.

This PDV-2331-based formulation had RI values of 1.52 at 400 nm and 1.49at 700 nm as well as k values of 0.0000-0.00031 for the visible lightwavelengths. The thermal degradation temperature of the composition was325° C. The formulation was spin-coated on a silicon wafer for 60seconds at 1,500 rpm, followed by baking for 60 minutes at 140° C. Thisformulation delivered a film thickness of 28,6 μm and had a pot life of1 day, and the formulation gelled on day 2.

Example 9 High-Molecular Weight Diphenylsiloxane-DimethylsiloxaneCopolymer-Based Formulation in the Presence of HMS-992 Crosslinker

High-molecular-weight (25,000-30,000 Daltons) vinyl-terminateddiphenylsiloxane-dimethylsiloxane (PDV-0331, 1000 cSt; Gelest,Arlington, Va. in the amount of 5 grams was blended with 0.0215 gram oftrimethylsilyl-terminated polymethylhydrosiloxane (HMS-992, Gelest,Arlington, Va.). This blend was stirred for 10 minutes at roomtemperature. Finally, 0.005 gram of undiluted, as-received SIP6831.2catalyst was added. After the catalyst was added, the blend was stirredfor 10 minutes at room temperature.

This PDV-0331-based formulation had RI values of 1.43 at 400 nm and 1.42at 700 nm, as well as k values of 0.0000-0.00114 for the visible lightwavelengths. The thermal degradation temperature of the composition was326° C. The formulation was spin-coated on a silicon wafer for 60seconds at 1,500 rpm, followed by baking for 60 minutes at 140° C. Thisformulation delivered a film thickness of 27.9 μm and had a pot life of7 days. Film thickness on day 4 was 28.74 μm and on day 7 it was 31.2μm. The formulation gelled on day 8.

Example 10 Diphenylsiloxane-Dimethylsiloxane Copolymer-Based Formulationin the Presence SL6040-D1 Inhibitor

This formulation was prepared by using the same reagents and amounts asin Example 7, with the exception of adding 0.005 gram of as receivedSL6040-D1 inhibitor to the blend before the catalyst was added. Afterthe inhibitor was added but before the catalyst was added, the blend wasstirred for 10 minutes at room temperature. The Brookfield viscosity at25° C. was 795 cP.

This PDV-2331-based formulation with inhibitor had RI values of 1.53 at400 nm and 1.49 at 700 nm as well as k values of 0.0000-0.00035 for thevisible light wavelengths. The thermal degradation temperature of thecomposition was 357° C. The formulation was spin-coated on a siliconwafer for 60 seconds at 1,500 rpm, followed by baking for 30 minutes at140° C. This formulation delivered a film thickness of 22.0 μm and itdelivered a 27.0 μm film thickness on day 21. The formulation gelled onday 22.

Example 11 Diphenylsiloxanc-Dimethylsiloxane Copolymer-Based Formulationin the Presence SL6040-D 1 Inhibitor

This formulation was prepared by using the same reagents and amounts asin Example 8, with the exception of adding 0.005 gram of as receivedsolution of SL6040-D 1 to the blend before the catalyst was added. Afterthe inhibitor was added but before the catalyst was added, the blend wasstirred for 10 minutes at room temperature. The Brookfield viscosity at25° C. was 820 cP.

This PDV-2331-based formulation with inhibitor had RI values of 1.52 at400 nm and 1.49 at 700 nm as well as k values of 0.0000-0.00034 for thevisible light wavelengths. The thermal degradation temperature of thecomposition was 339° C. The formulation was spin-coated on a siliconwafer for 60 seconds at 1,500 rpm, followed by baking for 30 minutes at140° C. This formulation delivered a film thickness of 22.0 pm anddelivered a 27.0 μm film thickness on day 21. The formulation gelled onday 22.

Example 12 High-Molecular Weight Diphenylsiloxane-DimethylsiloxaneCopolymer-Based Formulation in the Presence SL6040-D 1 Inhibitor

This formulation was prepared by using the same reagents and amounts asin Example 9, with the exception of adding 0.005 gram of as receivedsolution of SL6040-D1 inhibitor to the blend before the catalyst wasadded. After the inhibitor was added but before the catalyst was added,the blend was stirred for 10 minutes at room temperature. The Brookfieldviscosity at 25° C. was 950 cP.

This PDV-0331-based formulation with inhibitor had RI values of 1.44 at400 nm and 1.42 at 700 nm as well as k values of 0.0000-0.00037 for thevisible light wavelengths. The thermal degradation temperature of thecomposition was 332° C. The formulation was spin-coated on a siliconwafer for 60 seconds at 1,500 rpm, followed by baking for 30 minutes at140° C. This formulation delivered film thickness of 22.0 μm anddelivered a 27.0 μm film thickness on day 15. The formulation gelled onday 16.

Example 13 Diphenylsiloxane-Dimethylsiloxane Copolymer-Based Formulationin the Presence SL6040-D1 Inhibitor

This formulation was prepared by using the same reagents and amounts asin Example 10, with the exception of adding 0.05 gram of as receivedsolution of SL6040-D1 inhibitor to the blend before the catalyst wasadded. After the inhibitor was added but before the catalyst was added,the blend was stirred for 10 minutes at room temperature. The Brookfieldviscosity at 25° C. was 350 cP.

This PDV-2331-based formulation with inhibitor had RI values of 1.53 at400 nm and 1.49 at 700 nm as well as k values of 0.0000-0.00035 for thevisible light wavelengths. The thermal degradation temperature of thecomposition was 357° C. The formulation was spin-coated on a siliconwafer for 60 seconds at 1,500 rpm, followed by baking for 30 minutes at140° C. This formulation delivered a film thickness of 19.4 μm and onday 38 it delivered a 18.2 μm film thickness. On day 538, thisformulation delivered a film with 27.0 μm thickness and was ungelled.

Example 14 Diphenylsiloxane-Dimethylsiloxane Copolymer-Based Formulationin the Presence SL6040-D1 Inhibitor

This formulation was prepared by using the same reagents and amounts asin Example 11, with the exception of adding 0.05 gram of as receivedsolution of SL6040-D1 inhibitor to the blend before the catalyst wasadded. After the inhibitor was added but before the catalyst was added,the blend was stirred for 10 minutes at room temperature.

This PDV-2331-based formulation with inhibitor had RI values of 1.52 at400 nm and 1.49 at 700 nm as well as k values of 0.0000-0.00034 for thevisible light wavelengths. The thermal degradation temperature of thecomposition was 339° C. The formulation was spin-coated on a siliconwafer for 60 seconds at 1,500 rpm, followed by baking for 30 minutes at140° C., This formulation delivered a film thickness of 20.7 μm and onday 38 it delivered a 17.9 μm film thickness. On day 538, thisformulation delivered a film with 24.5 μm thickness and was ungelled.

Example 15 High-Molecular Weight Diphenylsiloxane-DimethylsiloxaneCopolymer-Based Formulation in the Presence SL6040-D1 Inhibitor

This formulation was prepared by using the same reagents and amounts asin Example 12, with the exception of adding 0.05 gram of as receivedsolution of SL6040-D1 inhibitor to the blend before the catalyst wasadded. After the inhibitor was added but before the catalyst was added,the blend was stirred for 10 minutes at room temperature.

This PDV-0331-based formulation with inhibitor had RI values of 1.44 at400 nm and 1.42 at 700 nm as well as k values of 0.0000-0.00037 for thevisible light wavelengths. The thermal degradation temperature of thecomposition was 332° C. The formulation was spin-coated on a siliconwafer for 60 seconds at 1,500 rpm, followed by baking for 30 minutes at140° C. This formulation delivered an initial film thickness of 17.8 μmand on day 38 it delivered a 22.6 μm film thickness.

Example 16 Polyphenylmethylsiloxane-Based Formulation in the Presence ofSL6040-D1 Inhibitor and SIP6831.2 Catalyst

This formulation was prepared by using the same reagents and amounts asin Example 5, with the exception of adding 0.05 gram of as receivedsolution of SL6040-D1 inhibitor to the blend before the catalyst wasadded. After the inhibitor was added but before the catalyst was added,the blend was stirred for 10 minutes at room temperature.

Films made from this PMV-based formulation had RI values of 1.56 at 400nm and 1.53 at 700 nm as well as k values of 0.0000-0.00159 for thevisible light wavelengths. The thermal degradation temperature of thecomposition was 223° C. The formulation was spin-coated on a siliconwafer for 60 seconds at 1,500 rpm, followed by baking for 30 minutes at140° C. This formulation delivered an initial film thickness of 17.8 μmand increased to 22.6 μm when another film was made as described aboveat day 38.

We claim:
 1. A method of forming an LED or other electronic ormicroelectronic structure, said method comprising: providing a substratehaving a surface; and forming a layer of a composition on said surface,said composition comprising a mixture of first and second siliconepolymers, wherein: said second polymer is different from said firstpolymer; and said composition has a pot life of at least about 24 hours.2. The method of claim 1, wherein said composition was prepared at leastabout 12 hours prior to said forming.
 3. The method of claim 1, whereinsaid substrate is selected from the group consisting of semiconductors,silicon, silicon dioxide, silicon nitride, aluminum gallium arsenide,aluminum indium gallium phosphide, gallium nitride, gallium arsenide,indium gallium phosphide, indium gallium nitride, indium galliumarsenide, aluminum oxide, glass, quartz, polycarbonates, polyesters,acrylics, polyurethanes, papers, ceramics, and metals.
 4. The method ofclaim 1, wherein said first polymer is selected from the groupconsisting of

where: each R₁ is individually selected from the group consisting ofalkylenes; and each of R₂ R₃, R₄, and R₅ is individually selected fromthe group consisting of alkyls, aromatics, and cyclic aliphatics.
 5. Themethod of claim 4, wherein said first polymer has a structure selectedfrom the group consisting of: (a) structure (I), where each of R₂ and R₃is phenyl; and each of R₄ and R₅ is —CH₃; and (b) structure (II), whereR₂ is —CH₃, and R₃ is phenyl.
 6. The method of claim 1, wherein saidsecond polymer is selected from the group consisting of

where each of R₆ and R₇ is individually selected from the groupconsisting of alkyls, aromatics, and cyclic aliphatics.
 7. The method ofclaim 6, wherein said second polymer has a structure selected from thegroup consisting of: (a) R₆ is phenyl; R₇ is —CH₃; and (b) each of R₆and R₇ is —CH₃.
 8. The method of claim 1, said composition furthercomprising an ingredient selected from the group consisting ofcatalysts, inhibitors, and mixtures thereof.
 9. The method of claim 8,wherein said composition comprises a catalyst, and said catalyst is aplatinum-containing catalyst.
 10. The method of claim 8, wherein saidingredient is an inhibitor that coordinates with platinum.
 11. Themethod of claim 8, further comprising heating said layer for asufficient time and to a sufficient temperature so as to cause saidpolymers to crosslink with one another so as to form a cured layer. 12.The method of claim 11, wherein the crosslinked polymers comprise thefollowing structure in the cured layer:


13. The method of claim 11, wherein said cured layer has a refractiveindex of at least about 1.5 at a wavelength of from about 375-1,700 nm.14. The method of claim 11, wherein said cured layer has a percenttransmittance of at least about 80% of light at a wavelengths of fromabout 375-1,700 nm and at a layer thickness of about 100 μm.
 15. An LEDor other microelectronic structure comprising: a substrate having asurface; and a layer of a composition on said surface, said compositioncomprising a mixture of first and second silicone polymers, wherein:said second polymer is different from said first polymer; and saidcomposition has a pot life of at least about 24 hours.
 16. The structureof claim 15 wherein said substrate is selected from the group consistingof semiconductors, silicon, silicon dioxide, silicon nitride, aluminumgallium arsenide, aluminum indium gallium phosphide, gallium nitride,gallium arsenide, indium gallium phosphide, indium gallium nitride,indium gallium arsenide, aluminum oxide, glass, quartz, polycarbonates,polyesters, acrylics, polyurethanes, papers, ceramics, and metals. 17.The structure of claim 15, wherein said first polymer comprises astructure selected from the group consisting of

where: each R₁ is individually selected from the group consisting ofalkylenes; and each of R₂ R₃, R₄, and R₅ is individually selected fromthe group consisting of alkyls, aromatics, and cyclic aliphatics. 18.The structure of claim 17, wherein said first polymer has a structureselected from the group consisting of: (a) structure (I), where each ofR, and R₃ is phenyl; and each of R₄ and R₅ is —CH₃; and (b) structure(II), where R₂ is —CH₃, and R₃ is phenyl.
 19. The structure of claim 15,wherein said second polymer comprises a structure selected from thegroup consisting of

where each of R₆ and R₇ is individually selected from the groupconsisting of alkyls, aromatics, and cyclic aliphatics.
 20. Thestructure of claim 19, wherein said second polymer has a structureselected from the group consisting of: (a) R₆ is phenyl; R₂ is —CH₃; and(b) each of R₆ and R₇ is —CH₃.
 21. The structure of claim 15, saidcomposition further comprising an ingredient selected from the groupconsisting of catalysts, inhibitors, and mixtures thereof.
 22. Thestructure of claim 21, wherein said composition comprises a catalyst,and said catalyst is a platinum-containing catalyst.
 23. The structureof claim 21, wherein said ingredient is an inhibitor that coordinateswith platinum.
 24. An LED or other microelectronic structure comprising:a substrate having a surface; and a cured layer on said surface, saidlayer comprising crosslinked polymers having a structure selected fromthe group consisting of:

where: each R₁ is individually selected from the group consisting ofalkylenes; and each of R₂, R₃, R₄, R₅, R₆, and R₇ is individuallyselected from the group consisting of alkyls, aromatics, and cyclicaliphatics.
 25. The structure of claim 24, wherein said cured layer hasa refractive index of at least about 1.5 at wavelengths of from about375 to about 1,700 nm.
 26. The structure of claim 24, wherein said curedlayer has a percent transmittance of at least about 80% of light atwavelengths of from about 375 to about 1,700 nm and at a cured layerthickness of about 100 μm.
 27. A composition comprising a mixture offirst and second silicone polymers and a catalyst, wherein: said secondpolymer is different from said first polymer; and said composition has apot life of at least about 24 hours.
 28. The composition of claim 27,wherein said first polymer comprises a structure selected from the groupconsisting of

where: each R₁ is individually selected from the group consisting ofalkylenes; and each of R₂ R₃, R₄, and R₅ is individually selected fromthe group consisting of alkyls, aromatics, and cyclic aliphatics. 29.The composition of claim 28, wherein said first polymer has a structureselected from the group consisting of: (a) structure (I), where each ofR₂ and R₃ is phenyl; and each of R₄ and R₅ is —CH₃; and (b) structure(TI), where R, is —CH₃, and R₃ is phenyl.
 30. The composition of claim27, wherein said second polymer comprises a structure selected from thegroup consisting of

where each of R₆ and R₇ is individually selected from the groupconsisting of alkyls, aromatics, and cyclic aliphatics.
 31. Thecomposition of claim 30, wherein said second polymer has a structureselected from the group consisting of: (a) R₆ is phenyl; R₇ is —CH₃; and(b) each of R₆ and R₇ is −CH₃.
 32. The composition of claim 27, saidcomposition further comprising an inhibitor.
 33. The composition ofclaim 32, wherein said inhibitor coordinates with platinum.
 34. Thecomposition of claim 27, wherein said catalyst is a platinum-containingcatalyst.